There are several ways to fabricate magnetoresistive (MR) sensors for read back of data on magnetic tape. In all cases, a bias method must be used in order to permit the sensor to operate in the linear portion of the MR curve. In some cases, two elements can be used at the same time, reading the same data, to reduce signal distortion by processing the signal differentially so that any nonlinearities arising from the shape of the MR curve are canceled out.
In a coupled element design, the two elements may be placed atop each other in close proximity. This allows the sensors to provide magnetic bias for each other, as well as providing the benefit of differential sensing capabilities for low distortion. The design has an added benefit of high output, since it is essentially two elements occupying the same space that one would under normal circumstances.
In order to achieve good performance at high densities, it is important that the head have good resolution characteristics. This, in turn, implies a narrow gap length and excellent gap surface condition. A narrow gap length is achieved by the intrinsic film design of the head and is determined by film thicknesses. Gap surface condition is determined by the mechanical lapping technique used, as well as the makeup of the films in the gap.
In the manufacture of a thin-film head, the read element is mechanically lapped to a fixed stripe height using techniques familiar to those skilled in the art. This processing and/or subsequent wear of the head when exposed to abrasive media can result in gouging, pulling out, smearing, or dishing of the gap area. In addition, the elements used to sense the recording data on tape can become recessed from the head surface. When such conditions occur, the linear density response (resolution) suffers.
As a result, there exists a need for a thin film coupled element high density read head design and method for manufacturing such a read head that overcome such problems and provide for good resolution characteristics. Such a read head and method for manufacturing that read head would provide for improving the condition of the gap area and ensuring that the MR sensors are not recessed from the head surface upon completion of the read head manufacturing process, and during read head operation.